1. Field of the Invention
This invention relates to a balance transformer and a backlight apparatus using the same, and more particularly, the invention relates to a balance transformer capable of driving a plurality of lighting units and a backlight apparatus using the same.
2. Description of the Prior Art
With the increase in the size of Liquid Crystal Display (LCD) panel, the backlight apparatus with a plurality of Cold Cathode Fluorescent Lamps (CCFLs) has been commonly used as the light source of the LCD panel.
Multi-lamp backlight apparatus is facing a critical issue: how the currents of the lamps can be kept substantially equal with each other to ensure that the light source that provides the LCD panel has stable and uniform illumination.
To solve the problem mentioned above, a Jin balance circuit for multi-lamp backlight apparatus was applied. Please refer to FIG. 1. FIG. 1 is a schematic diagram illustrating a backlight apparatus 1 with Jin balance circuit in the prior art. As shown in FIG. 1, the backlight apparatus 1 comprises ten lighting units 12. A balance transformer 10 is series connected to one lighting unit 12 in the Jin balance circuit, so the backlight apparatus 1 needs ten balance transformers 10 to ensure that the currents of the lighting units 12 are equal.
The increase in the size of LCD panel means that the required number of the lamps increases, and if the Jin balance circuit is used for balancing the currents flow through the lamps, the corresponding number of the transformers is also required. Besides, the size of the Printed Circuit Board (PCB) must be increased with the increase in the number of the balance transformers.
On the other hand, two polarities source is needed for driving the above-mentioned Jin balance circuit, however, a problem of isolating distance between two polarities lines arises with the present Jin balance circuit. The traditional solution discloses double-layer PCB and high-voltage jumpers for the increase in the isolating distance.
As described above, the increase in the number of the balance transformers, the increase in the size of the PCB, the increase in the number of the high-voltage jumpers, and the use of the double layers PCB will cause the cost of the backlight apparatus to arise.